Method for deploying a stent delivery system having a blowmolded holder

ABSTRACT

A method for deploying a stent delivery system having a blowmolded holder is provided. The stent is configured to expand from a first diameter to a second diameter. The holder is blowmolded to an inner surface of the compressed state. The holder contacts the inner surface and at least portions of side surfaces of the stent, and the holder and the stent have an interference fit therebetween. The deployment method includes delivering the compressed stent placed on the blowmolded holder and the holder into a predetermined deployment side. The deployment method further includes releasing the stent from interference with the holder and expanding the stent from the compressed stent to the expanded stent.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.12/336,172, filed Dec. 16, 2008, which is a divisional of U.S.application Ser. No. 11/076,568, filed Mar. 9, 2005, the disclosure ofwhich is herein incorporated by reference.

BACKGROUND

1. Technical Field

The invention relates to a method for deploying a stent delivery system.More particularly, the invention relates to a method for deploying astent delivery system having a blowmolded holder and interlocking andinterfering with a stent.

2. Related Art

Stents are commonly used to treat stenosis of various arteries. Whereblood vessels are clogged or narrowed by substances that restrict bloodflow, stents are delivered into such vessels and expanded to dilateblood vessels or maintain the dilated state of blood vessels. Expansionof stents may be made with or without the aid of a balloon.Balloon-expandable stents are expanded by inflating a balloon disposedbeneath a stent. On the other hand, self-expandable stents are capableof expanding without the use of a balloon. For this purpose,self-expandable stents are generally made from shape memory or springmetal, such as nitinol or stainless steel, so that self-expandablestents are able to expand from a compressed state upon removal ofpressures applied thereon.

Determining the proper stent to use is the first step to deploying astent. The proper stent is determined, in part, based on where a stentis to be deployed. For example, balloon-expandable stents are suitablefor coronary arteries, whereas self-expandable stents are more suitablefor peripheral arteries. However, the uses of balloon-expandable stentsand self-expandable stents often overlap, and each type of stent may beused in a variety of applications. In addition, long lesions or tandemlesions require long coverage. Multiple short stents or a single longstent may be implanted in long lesions or tandem legions.

Once deployed into a human body such as an artery, stents generallyremain as permanent implants. Accordingly, stents need to comply withhigh quality standards and minor manufacturing defects on the stents mayresult in the manufacturing rejection of the stents. Stents aregenerally manufactured through complicated and labor-intensiveprocesses. Stent manufacturing processes include laser cutting springmetal to form multiple, interconnected struts of a stent; sandblasting astent to eliminate debris generated from the laser cutting, andelectropolishing processes. Because of these processes, it is moredifficult to manufacture long stents with high precision and qualitythan short stents, in part because a long stent is prone tomanufacturing defects along the length compared to a short stent. Wherea long stent is rejected due to manufacturing defects, material costsand manufacturing expenses substantially increase.

Although defect-free long stents may be successfully manufactured,conventional stent delivery systems tend to improperly deploy longstents. This is particularly a problem in conventional stent deliverysystems where uneven, high forces are applied at the proximal end topush a long stent out of the delivery system upon deployment. FIGS. 1Aand 1B illustrate a conventional stent delivery system 1 for aself-expandable stent 10. The stent delivery system 1 includes theself-expandable stent 10, a holder 18 and a sheath 8. The sheath 8radially constrains the stent 10 during delivery and is retracted whenthe stent 10 needs to be deployed as shown in FIG. 1B. The holder 18 isdisposed beneath the stent 10 and supports the stent 10 during delivery.The stent 10 expands from a compressed state to an expanded state asshown in FIGS. 1A and 1B. The stent delivery system 1 is mounted on oneend of a delivery catheter 50. The delivery catheter 50 has an outertube 8 functioning as a sheath and a core 4, which longitudinallyextends from a proximal end 20 to a distal end 22. The core 4 isconnected to a hub 2 at the proximal end 20 and to a holder 18 at thedistal end 22. The outer tube 8 is connected to a handle 7. A physiciandeploys the stent 10 by pulling the handle 7 towards the hub 2. As theouter tube 8 is retracted by pulling the handle 7, the stent 10 isexposed and starts expanding. The stent 10 is fully deployed when thehandle 7 reaches the hub 2. However, the stent delivery system 1 oftenexperiences problems when the stent to be deployed is long. Deploymentof long stents often requires high concentrated force particularly atthe proximal end 22 to push the long stent out of the stent deliverysystem 1. This frequently results in improper or inaccurate deploymentof the long stent.

In addition to improper deployment of long stents, the stent deliverysystem 1 presents other disadvantages as well. One disadvantage is thatit is difficult to reduce the size of the stent delivery system 1. It isgenerally desirable for most stent delivery systems to have a lowprofile. Stent delivery systems that have lower profiles reduce possibledamage to blood vessels during delivery and deployment of the stent.Further, stent delivery systems with lower profiles may be able to getto small and/or tortuous blood vessels. However, the sheath 8substantially increases the overall profile of the stent delivery system1. When the sheath 8 is retracted, the stent 10 may unexpectedly and/oruncontrollably move. As previously stated, because the stent 10 is madefrom spring metal, it tends to expand upon retraction of the sheath 8.This makes it difficult for physicians to accurately position the stent10. Various attempts have been made to address this problem. Forexample, structures such as rings and shafts may be added to an innerholder adjacent the proximal end. These structures may engage theproximal end of a stent in order to longitudinally restrain the stent.When the sheath is retracted, the distal end of the stent is firstexposed into the blood vessel. Because the proximal end of the stent istemporarily restrained by these structures, the stent may not abruptlymove in response to the retraction of the sheath. However, thestructures, such as rings and shafts, may be counterproductive toaccurate deployment of stents because they trap the stent which must beexpanded. In addition, such structures require sophisticated design,which increases manufacturing expenses.

The stent delivery system 1 may not be optimal for delivering anddeploying drug coated stents. The stent 10 may include drug coatings onthe outer surface thereof. Drugs may be coated on the stent 10 forvarious purposes. For example, drugs may prevent the formation of scartissue on the vessel walls or reduce restenosis. Contrary to thesebenefits, some drug coatings may cause unfavorable consequences ifapplied improperly. For example, drugs, such as scar prevention drugs,may be highly incompatible with blood. Thus, when drugs that are coatedon the stent 10 come into contact with blood, the drugs may causeproblems such as blood clots. For this reason, it is desirable thatdrugs are disposed only on the outer surface of the stent 10. Becausethe outer surface of the stent 10 is pressed against the vessel wallsupon expansion, blood does not flow between the outer surface of thestent 10 and the vessel walls. However, the conventional stents 10usually contain drug coatings on the sides and inner surfaces which comeinto contact with the blood. Drug coating material is typically sprayedon a stent 10 when it is in an expanded state. Because the stent 10 isself-expandable, it is generally not possible to spray the drug coatingmaterial on the compressed stent 10 since the outer surface of the stent10 is constantly pressed against the inner surface of a transfer tube ora sheath 8 when it is compressed. When the drug coating material issprayed on the expanded stent 10, it easily covers the sides and insidesurfaces of the stent 10 through the openings between the struts of thestent 10. Further, the stent has relatively large openings when it isexpanded. This reduces the efficiency of spraying because a substantialamount of sprayed drugs passes through the openings.

Even if drugs may be adequately sprayed on the expanded stent 10, theymay be lost in the course of manufacturing (e.g., loading into thedelivery system) and the deployment processes of the stent 10. The stent10 must be compressed, for example, by rolling it down to a smallerdiameter. During this compression process, shear force or mechanicaltrauma is applied to the stent 10 and a substantial amount of the drugcoating may be lost. Further, when the stent 10 is pushed into thesheath 8 and the sheath 8 is later retracted rearward to deploy thestent 10, a substantial portion of the drug coating may be lost.Accordingly, there is a need for a stent delivery system that overcomesthe foregoing drawbacks.

SUMMARY

The invention provides a stent delivery system that comprises at leastone stent and a holder. The stent is expandable from a compressed stateto an expanded state. The holder interlocks and interferes with thestent in the compressed state. An outer diameter of the holder contactsan inner diameter of the stent. For example, the holder may beblowmolded onto an inner surface of the stent in the compressed state.Various other processes are possible to interlock the stent with theholder. The stent delivery system may or may not include sheath. In oneembodiment, the sheath may radially constrain the stent. In otherembodiment, the sheathless stent delivery system may include astimulator configured to apply a predetermined force to an inner surfaceof the holder.

In yet another embodiment, a stent delivery system includes a holderhaving a pattern or impression. The pattern or impression interlocks andinterferes with the stent in the compressed state. The pattern orimpression may be formed by a blowmolding process. The pattern orimpression does not extend through the stent and contacts side surfacesof the stent. Alternatively, or additionally, the pattern or impressionmay extend through the stent in the compressed state.

In yet another embodiment, a stent delivery system includes at least onestent having a plurality of radial openings. The radial openings aredefined in part by side surfaces of the stent. The stent delivery systemfurther includes a holder having a portion extended from an outerdiameter of the holder. The portion of the holder contacts the sidesurfaces of the stent. Accordingly, the portion restricts longitudinalmovement of the stent relative to the holder. When an expansion force ofthe stent exceeds the restraining force of the holder, the stent isexpanded to the expanded state. The stent delivery system furtherincludes a sheath radially constraining the stent. Alternatively, oradditionally, the stent delivery system includes no sheath. Instead ofthe sheath, the portion of the holder further extends around a portionof an outer diameter of the stent. Thus, the portion of the holder mayradially constrain the stent. This sheathless stent delivery systemfurther includes means for stimulating an inner surface of the holder,thereby to release the stent from the holder. The stent delivery systemfurther includes a tip attached to the holder at one end of the stent.The holder is made from one of polyethylene terephathalate, crosslinknylon and irradiated polyethelene.

In yet another embodiment, a sheathless stent delivery system includesat least one stent and a holder blowmolded onto an inner surface of thestent in the compressed state. The stent includes a plurality of strutsinterconnected with one another to form multiple openings therebetween,and the holder includes a plurality of extensions that extend throughthe multiple openings of the stent. The holder wraps around a portion ofan outer surface of the stent, thereby to retain the stent in thecompressed state. The sheathless stent delivery system further includesa stimulator adapted to apply a predetermined force to an inner surfaceof the holder, thereby to release the stent from the holder. Forexample, the stimulator includes a ball that has a diameter larger thanan inner diameter of the holder. The ball is attached to a wire thatextends through a hollow interior of the holder. The ball is configuredto stimulate the inner surface of the holder as the ball is pulledrearward. The ball is made from a rigid material such as steel. Thesheathless system may have an outer diameter smaller than about 0.0540inch.

In yet another embodiment, a sheathless stent delivery system includes acontainer positioned inside the holder and storing a liquid suppliedthereto. Preferably, the liquid may be compatible with blood. The stentis released from the holder in response to increased pressure of thecontainer. For example, the container may include an occluder.

In yet another embodiment, a stent delivery system includes a holder anda plurality of stents longitudinally arranged one after another. Theplurality of stents are expandable from a compressed state and anexpanded state. The holder is blowmolded onto an inner surface of stentsin the compressed state. The plurality of stents may be different insize, length and/or flexibility. At least one of the plurality of stentsmay include a drug coating.

In yet another embodiment, the invention provides a method for deployinga stent disposed on a blowmolded holder. The method includes deliveringa stimulator attached to a wire to a predetermined deployment site anddelivering the compressed stent and the holder to the deployment site bythreading the wire through an interior of the holder. The wire mayextend from a proximal end to a distal end. The method further includesstimulating an inner surface of the holder by retracting the stimulatortoward the proximal end. A diameter of the stimulator is larger than aninner diameter of the holder. The method also includes releasing thestent from the holder, thereby to expand the stent to the expandedstate.

In yet another embodiment, a deploying method includes delivering thecompressed stent and the holder into a predetermined deployment site anddelivering a container into the deployment site and positioning thecontainer inside the holder. The deployment method further includessupplying a quantity of liquid into the container and stimulating aninner surface of the holder in response to an increased pressure of thecontainer. The increased pressure is responsive to supply of the liquid.The method further includes releasing the stent from the holder, therebyto expand the stent to the expanded state.

In yet another embodiment, a deploying method includes (a) deliveringthe plurality of stents in the compressed state and the holder to apredetermined deployment site and (b) retracting the sheath toward aproximal end to the extent that a first stent is exposed wherein thefirst stent is disposed distally adjacent a distal end. The methodfurther includes (c) expanding the first stent from the compressed stateto the expanded state, (d) retracting the sheath toward the proximal endto the extent that a second stent is exposed wherein the second stent isdisposed proximally adjacent the first stent and (e) repeating the stepof (a)-(d) until remaining stents are expanded.

In yet another embodiment, a method for manufacturing a stent deliverysystem is provided. The stent delivery system includes compressing thestent to the first diameter, inserting the stent into a first tube andplacing a second tube inside the first tube and inside an inner diameterof the stent. The second tube is airtight. The manufacturing methodfurther includes applying pressure and heat suitable to the second tube,thereby to blowmold the second tube against the stent. The methodfurther includes cooling down the first tube, the stent and the secondtube without any pressure. The method also includes inserting the stentand the second tube into a sheath as the first tube is removed, andsealing an end of the second tube during blowmolding and removing theseal after the blowmolding.

The pressure may range between 30 psi and 90 psi. The heat may rangebetween 200° F. and 280° F. Specifically, the pressure may range between35 psi and 45 psi and the heat ranges between 210° F. and 220° F. Morespecifically, the pressure is about 40 psi and the heat ranges between210° F. and 220° F. In other embodiment, the pressure ranges between 85psi and 95 psi and the heat ranges between 230° F. and 280° F. Morespecifically, the pressure is about 90 psi and the heat is about 250° F.

In yet another embodiment, a method for manufacturing a sheathless stentdelivery system is provided. The method includes compressing the stentfrom an expanded state to a compressed state, blowmolding the holderagainst the stent by applying suitable heat and pressure, and applying adrug coating material on an outer surface of the stent in the compressedstate. The drug coating material does not cover an inner surface andside surfaces of the stent. The step of applying the drug coatingmaterial includes spraying the drug coating material.

The invention provides a stent delivery system having a low profile. Thestent delivery system also minimizes damage to blood vessels andproperly deploys long stents. The stent delivery system furtheraddresses specific needs of deployment sites, such as blood vessels.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereferenced numerals designate corresponding parts throughout thedifferent views.

FIGS. 1A and 1B depict a conventional stent delivery system.

FIG. 2 depicts a first embodiment of a stent delivery system.

FIG. 3 illustrates one embodiment of a method for manufacturing thestent delivery system of FIG. 2.

FIG. 4 illustrates one embodiment of a method for deploying the stentdelivery system of FIG. 2.

FIG. 5 depicts a second embodiment of a stent delivery system.

FIG. 6 depicts a third embodiment of a stent delivery system.

FIG. 7A illustrates one embodiment of a method for deploying the stentdelivery system of FIG. 5.

FIG. 7B illustrates another embodiment of the method for deploying thestent delivery system of FIG. 6.

FIG. 8 depicts an exemplary drug coating process.

FIG. 9 depicts an enlarged view of a portion of the stent deliverysystem of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows a first embodiment of a stent delivery system according tothe invention. The stent delivery system 100 includes a first stent 106,a second stent 108, a sheath 110 and a holder 104. At a distal end ofthe first stent 106, a distal tip 102 is coupled to the holder 104. InFIG. 2, two stents 106 and 108 are delivered by the stent deliverysystem 100, but delivery of more or less stents is possible. The firststent 106 and the second stent 108 are self-expandable stents,respectively, and expand from a compressed state to an expanded state.The stents 106, 108 have a plurality of radial openings and the radialopenings are defined in part by side surfaces of the stents 106, 108.The sheath 110 radially constrains the stents 106, 108 to keep thecompressed state. The holder 104 interlocks and interferes with theinner surfaces of the stents 106, 108. Specifically, the holder 104 hasa portion extended from its outer diameter and that portion contacts theside surfaces of the stents 106, 108.

For interlocking and interference, the holder 104 has a first pattern orimpression as shown in FIG. 2. The stents 106, 108 may be press-fit orfriction-fit into the first pattern of the holder. This first pattern orimpression of the holder 104 does not extend through the radial openingsof the stents 106, 108. Rather, it contacts the side surfaces of thestents 106, 108. To form the first pattern or impression, the holder 104may be blowmolded. The manufacturing of the holder 104 is not limited tothe blowmolding process and various processes are possible. Forinstance, processes such as casting, injection molding, milling,etching, lithography, electrical discharge machining and laser machiningmay be used.

When the first pattern or impression of the holder 104 is formed byusing the blowmolding process, the holder 104 may precisely conform toinner diameters of the stents 106, 108, as will be described below. Aself-expandable stent such as the stents 106, 108 is typicallycompressed to have a predetermined compressed diameter, regardless oftypes or sizes of the stents. Although the first stent 106 and thesecond stent 108 have different diameters upon expansion, they may becompressed to have the same diameter. Accordingly, the holder 104 maysupport the compressed stents 106, 108, although the stents 106, 108 maybe of different types and have different lengths and/or diameters. Thetip 102 may be bonded to the holder 104. The distal tip 102 mayfacilitate navigation of tortuous arteries and vessels during thedelivery of the stents 106, 108.

The stent delivery system 100 is manufactured as shown in FIG. 3. Theself-expandable stents 106 and 108 are compressed for delivery at block310. For example, the stents 106 and 108 may be mechanically rolled downto be compressed. Alternatively, or additionally, other knowncompression methods may be used. Subsequently, the compressed stents106, 108 are slid into a first tube (block 320). The first tube may bemade from any material that has a higher plastically melting thresholdthan blowmoldable materials. For example, the first tube may be madefrom steel. The first tube is also made from polytetrafluoroethylene(“PTFE”). PTFE is radially flexible and longitudinally stiff, andtherefore, it is frequently used to form a tube that is used formanufacturing stent delivery systems. At the next block 330, a secondtube is inserted into the first tube and inside the inner diameters ofthe stents 106, 108. The second tube may be made from any material thatis capable of being blowmolded. For example, polyethylene terephthalate(“PET”), crosslink nylon or irradiated polyethylene may be used to formthe second tube. The second tube may have a thick wall and is smallenough in diameter to fit inside of the stents 106, 108. The second tubeis a pre-form of a final structure, so that it has a substantiallysimilar shape as that of the final structure. By way of example, thesecond tube may have an outer diameter, 0.050±0.001 inch and an innerdiameter, 0.021±0.001 inch. Alternatively, or additionally, the secondtube may be thin. The thin second tube may be, in particular, suitablefor a stent with a high radial force.

As a process of manufacturing the holder 104, a blowmolding process isdescribed in detail. However, various other processes are available.After the second tube is inserted, it is sealed at the end so that it isairtight (block 340). Next, heat and pressure suitable for blowmoldingis applied to the second tube (block 350). For example, heatingtemperature ranges may be between 200° F. to 240° F. More specifically,the heating temperature may range from 210° F. to 220° F. Air pressureranges between 35 psi and 45 psi, and more preferably, may be about 40psi. Under the heat and pressure, the second tube is blown out and ismolded to the inner surface of the stents 106, 108. The stents 106, 108include multiple struts that are made from shape memory or spring metalwhich are interconnected with one another. A plurality of radialopenings are formed between the struts and defined in part by sidesurfaces of the stents 106, 108. The struts and the radial openings mayform the inner surface of the stents 106, 108. The second tube is moldedto the struts of the stents 106, 108 and is tightly fitted into theinner diameter of the stents 106, 108. As previously described, theinner diameter of the second tube before the blowmolding may be0.021±0.001. However, after the blowmolding, the inner diameter of thesecond tube may be enlarged to have a diameter of about 0.035 to 0.040inch. The blowmolding process may take a few seconds. For example, itmay take about 12 seconds. As a final step (block 360), the first tube,the stents 106, 108 and the second tube are cooled down. While the firsttube, the stents 106, 108 and the second tube are exposed to heating andpressure for the blowmolding process, the second tube and the stents106, 108 push against the first tube. The first tube may be separatedfrom the second tube and the stent by cooling it down. The cooling downprocess may take a few seconds, for example, 5-10 seconds.

After the cooling down process, the stents 106, 108 and the holder maybe released from the first tube. The stents 106, 108 and the holder 104are then slid into the sheath 110 and at the same time, the first tubeis removed by pulling it off the stents 106, 108 (at block 370). The tip102 may be coupled to the holder 104 at the distal end. Alternatively,or additionally, the tip 102 may be coupled to the holder 104 before theholder 104 is slid into the sheath 110. The stent delivery system 100 iscompleted and mounted on one end of a delivery catheter for delivery anddeployment of the stents 106, 108. The delivery catheter may have thestructure similar to the delivery catheter 50 as shown in FIGS. 1A and1B.

Referring to FIG. 4, delivery and deployment of the stents 106, 108 aredescribed. To deliver the stents 106, 108, the Seldinger techniques maybe used at block 430. The Seldinger techniques may involve a needle, aguidewire and a dilator. The stent delivery system 100 is introducedthrough the dilator and removed therefrom later. When the stent deliverysystem 100 arrives at the desired deployment site, a physician startsretracting the sheath 110 rearward, i.e., toward the proximal end (block440). As the sheath 110 is retracted, the first stent 106 becomesexposed and is released. The stent 106 maintains its compressed stateuntil the sheath 110 is sufficiently retracted (block 450). Because theholder 104 is molded to the first stent 106, the holder temporarilyrestrains a longitudinal movement of the first stent 106. Consequently,abrupt movement of the first stent 106 upon retraction of the sheath 110is restrained by the holder 104, which allows the physician some time toretract the sheath 110 without being concerned about the abrupt movementof the first stent 106 (block 450). When expansion force of the firststent 106 exceeds the restraining force of the holder 104, the firststent 106 starts to expand. The sheath 110 is then retracted further toexpose the second stent 108 at block 460. The second stent 108 isdeployed in the same manner as the first stent 106 in block 470. Afterthe stents 106, 108 are fully expanded, the holder 104 is removed fromthe deployment site at block 480.

Although FIGS. 2-4 illustrate delivery and deployment of the two stents106 and 108, it is possible to deploy a single long stent or multiplestents with the stent delivery system 100. Where multiple stents aredeployed, each stent may have different diameters, special coatings,radial forces and/or flexibility characteristics or combinationsthereof. Where an artery is curved or has nonuniform diameters along thelength, implanting multiple stents having different diameters andlengths may optimize the treatment of such an artery. For example, if acertain vessel has different diameters along its length, stentscorresponding to the different diameters of the vessel may be arrangedand deployed in the vessel. Further, if a portion of the vessel needs acertain treatment, a stent to be deployed in that portion may includeeffective drug coatings. Multiple stents may be arranged to addressdifferent needs of various deployment sites. This results in optimizedstenting that is specifically tailored to the needs of deployment sites.Furthermore, where a single, long stent is deployed, the holder 104uniformly restrains the long stent along the longitudinal direction as aresult of the blowmolding. Thus, the pressure is evenly distributedalong the length of the long stent and does not concentrate on thedistal end of the long stent. Accordingly, proper and accuratedeployment of the long stents is possible. The stent delivery system 100also substantially reduces the waste associated with the complicated andcostly manufacturing processes of long stents.

FIG. 5 shows a second embodiment of a stent delivery system. Unlike thefirst embodiment, the stent delivery system 500 is a sheathless stentdelivery system. The stent delivery system 500 has no sheath such as thesheath 110. Two stents 106, 108 are delivered by the stent deliverysystem 500, but more or less stents may be delivered. A holder 502 has asecond pattern or impression that extends through the openings of thestents 106, 108, which are formed by multiple struts. The height of theextensions 507 that extend through the openings is adjustable bychanging the heat and/or pressure that is applied during the blowmoldingprocess, as will be described in detail below. The second pattern orimpression is different from the first pattern or impression shown inFIG. 2 in that the second pattern or impression extends through theopening of the stents 106, 108. The first pattern or impressioninterlocks or interferes with the stents 106, 108, but it does notextend further. The first pattern may contact side surfaces of thestents 106, 108. To the contrary, the second pattern or impression maypartially radially wrap around the stents 106, 108 and press over edgesof the stents 106, 108. A tip such as the tip 102 in FIG. 1 may beattached to the holder 502.

The stent delivery system 500 further includes a stimulator such as aball 504 attached to a wire 506. The wire 506 passes through the centerof the stent delivery system 500 as shown in FIG. 5. The ball 504 may bemade from any material that is rigid such as steel. The ball 504 may besolid and has a throughhole inside. Alternatively, the ball 504 may behollow inside. The ball 504 has a diameter that is about the same as theinner diameter of the stents 106, 108 but is not smaller than the innerdiameter of the holder 502. In this embodiment, the ball 504 is used asa stimulator, but various other structures are possible. As long as thestructure has a diameter that is not smaller than the inner diameter ofthe holder 502, the shape of such structure is not limited to a ballshape. The ball 504 provides appropriate pressure, stimuli or force tothe holder 502. Because the holder 502 extends radially through thestents 106, 108, and more specifically, through the radial openings ofthe stents 106, 108, it securely restrains the stents 106, 108 fromexpanding. Accordingly, apart from the nature of the stents 106, 108,i.e., the tendency to expand, a separate force and/or pressure isrequired to release the stents 106, 108 from the holder 502. As the ball504 passes through the interior of the holder 502 by pulling back on thewire 506, it continuously stimulates the inner walls of the holder 502.

Alternatively, or additionally, the ball 504 may be taken in and pushedthrough the interior of the holder 502. The stent delivery system 500 isalready disposed within the blood vessel. The ball 504 attached to thewire 506 may be moved to the blood vessel and pushed through theinterior of the holder 502.

The requisite force may differ depending on the flexibility of theholder 502. If the holder 502 is very flexible, a minimum amount ofpressure allows the stents 106, 108 to be released from the holder 502.If the holder 502 is more or less rigid, a relatively high pressure maybe required. The ball 504 may touch, strike and/or interfere with theinner surface of the holder 502.

The manufacturing process of the stent delivery system 500 is in manyways similar to that of the stent delivery system 100. The stents 106,108 are compressed and inserted into the first tube made from, forexample, PTFE. Then, the second tube which will become the holder 502 isinserted into the first tube and inside the inner diameters of stents106, 108. The end of the second tube is sealed so that it is airtight,and the second tube is blowmolded to the stents 106, 108 by applyingappropriate heat and pressure. As noted above, the holder 502 may beformed with various other processes. Unlike the stent delivery system100, the stent delivery system 500 typically requires higher pressureand heat than the stent delivery system 100. This is because someportions of the holder 502 are forced to extend through the openings inthe stents 106, 108. For example, pressure applied to the stent deliverysystem during blowmolding ranges from about 85 psi to 95 psi. Morepreferably, pressure may be about 90 psi. Heating temperature rangesbetween 230° F. and 280° F., and more preferably, is about 250° F. Byadjusting the pressure, temperature or the combination thereof, it ispossible to control how far the holder 502 extends radially through thestents 106, 108.

The manufacturing process further allows the stent delivery system 500to have a compact and tight design. A stent is subject to anelectropolishing process that rounds corners off. However, some residualcorners may be present even after the electropolishing process. Theholder 502 wraps around edges and/or corners of the stents 106, 108, andtherefore, the stent delivery system 500 may not interfere with even asmall, tortuous blood vessel during the delivery. Further, by radiallypressing the stents 106, 108 with the holder 502, the stent deliverysystem 500 may have a tighter, compact and low profile.

The ball 504 and the wire 506 may be manufactured separately from thestent delivery system 500. The ball 504 is solid and has a mainthroughhole. The wire 506 may be connected through the main throughhole.The wire 506 may be a guidewire and no additional wire may be required.Alternatively, or additionally, the ball 504 may be hollow and the wire506 is soldered to the end of the ball 504 as shown in FIG. 3. The ball504 may be attached to a distal end of a guidewire.

Once the stent delivery system 500 is manufactured, the stents 106, 108are delivered and deployed. Referring to FIG. 7A, operations of thestent delivery system 500 are described. FIG. 7A illustrates oneembodiment of a method for deploying the stents 106, 108 using the stentdelivery system 500. The method illustrated in FIG. 7A uses theSeldinger techniques at block 720. The ball 504 and the wire 506 may beused to deploy the stents 106, 108. In this case, the ball 504 bonded tothe wire 506 is inserted into a predetermined deployment site, forexample, a blood vessel. In this embodiment, a guidewire may not beused. Alternatively, or additionally, it is possible to thread the ball504 over a guidewire and insert it into the deployment site. In otherembodiment, the ball 504 may be taken in and pushed through the bloodvessel. Physicians may choose whether the ball 504 is introduced priorto or after the introduction of the stent delivery system 500, dependingon their preferences, deployment sites, or many other factors.

The stent delivery system 500 is mounted on one end of a deliverycatheter. The delivery catheter is inserted over the wire 506 until thestents 106, 108 arrive at the deployment site (block 730). Because asheath is not a part of the stent delivery system 500, there is noretraction of a sheath. Instead, the ball 504 is pulled back to applyappropriate force to the holder 502. The ball 504 is retracted rearwardby pulling the wire 506 (block 740). Alternatively, or additionally, theball 506 may be taken in and pushed through. Due to the movement of theball 504, the inner surface of the holder 502 is stimulated and thestents 106, 108 are released from the holder 506 (block 750). Oncereleased from the holder 502, the stents 106, 108 start to expand atblock 760. After the stents 106, 108 are expanded, the holder 502 isremoved from the blood vessel, leaving the stents 106, 108 (block 780).

FIG. 6 is a third embodiment of a stent delivery system. A stentdelivery system 600 includes the stents 106, 108 and the blowmoldedholder 502 having the extensions 507 like the stent delivery system 500.However, instead of the ball 504, the stent delivery system 600 furtherincludes a container device 610. In the stent delivery system 600, acertain type of liquid, which is preferably compatible with blood, maybe used to provide pressure to the holder 502. Such liquid may be, forexample, saline or carbon dioxide. To supply the liquid, a syringe (notshown) may be connected to a delivery catheter and introduce the liquidinto the delivery catheter. Alternatively, handle-turned or knob-turnedpressure devices may introduce the liquid into the delivery catheter.The container device 610 may be an artery or vessel occluder. Thecontainer device 610 may be required to be disposed inside the holder502. The container device 610 may block the liquid from flowing into ablood vessel. As the liquid flows into the container device 610,pressure builds up inside the container device as indicated by smallarrows in FIG. 6. This built-up pressure provides pressure or stimuli onthe inner surface of the holder 502 and makes the holder 502 release thestents 106, 108.

FIG. 7B illustrates another embodiment of a method for deploying stents106, 108 by using the sheathless stent delivery system 600. Inparticular, as a stimulator, a certain type of liquid is used tostimulate the inner surface of the holder 502. At block 722, the stentdelivery system 600 may be introduced using the Seldinger techniques toa deployment site. The stent delivery system 500 is delivered through adelivery catheter (block 732). After the stent delivery system 500 isdelivered to the deployment site, the container device 610 is insertedover the guidewire and positioned inside of the inner surface of theholder 742 at block 742. Alternatively, or additionally, the containerdevice 610 may be inserted before the stent delivery system 500 isdelivered. When the container device 610 is placed properly, a certaintype of liquid is provided through the delivery catheter to thecontainer device at block 752. Due to the flow of the liquid, the innerpressure of the container device 610 increases and stimulates the innersurface of the holder 502 at block 752. This stimuli, force or pressureby the container device onto the inner surface of the holder 502 makesit possible for the stents 106, 108 to be released from the holder 502at block 762. As a result, the stents 106, 108 expand and the holder 502is removed from the deployment site (block 782).

As previously stated, the stent delivery system 500 and 600 do not needa sheath, and therefore, has a lower profile. The stent delivery system500, 600 have a substantially reduced outer diameter, for example,0.040˜0.060 inches due to absence of a sheath. Specifically, the stentdelivery system 500, 600 may have an outer diameter smaller than 0.054inch. Accordingly, damage to blood vessels which may arise duringconventional stenting process may be substantially reduced andmanufacturing labor and costs may also be minimized. Furthermore, thestent delivery system 500, 600 provide the same advantages that areprovided by the stent delivery system 100.

Another advantage is that the stent delivery system 500, 600 aresuitable for delivery and deployment of drug coated stents. FIG. 8 showsone embodiment of a drug coating process for the sheathless stentdelivery systems 500, 600. As shown in FIGS. 5 and 6, the sheathlessstent delivery systems 500, 600 include the compressed stents 106, 108and the blowmolded holder 502. The blowmolded holder 502 radially wrapsaround the stents 106, 108. More specifically, the extensions 507 of theholder 502 securely retain the stents 106, 108. Drug coating materialmay be applied to the outer surfaces of the compressed stents 106, 108as shown in FIG. 8. For example, the drug coating material may besprayed on the compressed stents 106, 108. Alternatively, drug coatingmaterials may be sprayed on the expanded stents 106, 108 if necessary.In other embodiments, only one stent 106 or 108 may be sprayed.

Drug coating materials may include a drug only, a drug mixed with apolymer, or any type of a drug carrier or binder carrying a drug. Thedrug coating material may have multiple layers including one layer of adrug or one layer of a polymer. The drug carrier or binder may bedisposed underneath or on the top of the drug layer. Drugs coated on thestents 106, 108 may include drugs that prevent scar formation,restenosis, etc. These drug coatings may or may not be compatible withblood. For example, drugs for prevention of scar formation may not becompatible with blood. By way of example, drug coating materials mayinclude drugs such as Batimastat, Angiopeptin, ABT 578, Dexamethasone,17 beta estradiol, Paclitaxel, Myfortic, Endothelial progenitor cells(EPC), surface antibodies, Pimecrolimus, Absorbable MG-alloy, QP-2Paclitaxel derivative, Everolimus, Sirolimus, Biolimus A7 Biolimus A9,Viral proteins, Actinomycin D, Tranilast, Rapamune, Tacrolimus, C-myc,Cyclosporine, EQs, CD-34 antibody, and/or Tacrolimus. Detaileddescriptions on drug coating materials may be found in U.S. Pat. Nos.5,380,299; 5,609,629; 5,824,049; 5,873,904; 6,096,070; 6,299,604;6,530,951; 6,730,064; 6,774,278 and U.S. Patent Publication Nos.2003/28243; 2003/28244; 2003/36794 and 2004/47909, which areincorporated herein by reference.

As shown in FIG. 8, the blowmolded holder 502 tightly wraps around theinside of the stents 106, 108. Specifically, the holder 502 has aportion extended from an outer diameter thereof, i.e., the extensions507. The extensions contact the side surfaces of the stents 106, 108such as side surfaces 910 shown in FIG. 9 and restrict longitudinalmovement of the stents 106, 108 relative to the holder 502. Further, theextensions 507 of the holder 502 extend around a portion of an outerdiameter of the stents 106, 108 and radially constrain the stents 106,108. As a result, no sheath is required for delivery and deployment ofthe stents 106, 108. Without a sheath, the stents 106, 108 remaincompressed and are able to be deployed. Sprayed drug coatings may beapplied only on the outer surface of the stents 106, 108. Because theouter surfaces of the stents 106, 108 are pressed against vessel walls,blood does not flow between the outer surfaces of the stents 106, 108and the vessel walls. FIG. 9 depicts an enlarged view of a portion ofthe stent delivery system 500, 600. The stents 106, 108 include the sidesurfaces 910 disposed at its radial openings. The radial openings aredefined in part by the side surfaces. The stents 106, 108 also haveinner surfaces 920. The drug coating material may be precisely sprayedon the outer surfaces of the stents 106, 108 and does not spread to thesides 910 and/or inside surfaces 920 of the stents 106, 108. Unlike theouter surface, the sides 910 and/or inside surfaces 920, 930 of thestents 106, 108 may contact blood. Therefore, even if the drug coatingsare incompatible with blood, no restenosis, blood clots or relatedproblems occur because the drugs do not reside on the sides 910 and/orthe inside surfaces 920, 930 of the stents 106, 108. Further, becausethe drug coatings may be sprayed on the compressed stents 106, 108, lossof the drug coatings through large openings of the expanded stents 106,108 and compression processes of the stents 106,108 may be substantiallyminimized. In addition, the drug coatings are not lost due to a sheathsince the stent delivery system 500 is sheathless.

The advantages of the effective drug coatings may be achieved regardlessthe holder 502. The holder 502 may be made from materials that have highor low surface tensions. Upon application of the drug coatings, theholder 502 with high surface tension may keep drug coatings thereon andloss of the drug coatings may be minimized. Alternatively, the holder502 with low surface tension may not keep the drug coatings thereon.Instead, the drug coatings may flow onto the stents 106, 108 interferedwith the holder 502. Loss of the drug coatings may be again reduced.

Although various embodiments have been described in connection with astent delivery system, the invention is not limited to the describedembodiment of the stent delivery system. The invention may be applicableto other medical systems or methods that involve implantation of adevice or structure like a stent. The application of the invention maybe more useful if the device or structure has characteristics ofself-expansion.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of theinvention. Accordingly, the invention is not to be restricted except inlight of the attached claims and their equivalents.

1. A method for deploying a stent, wherein the stent is configured toexpand from a compressed state to an expanded state, comprising:delivering the compressed stent placed on a blowmolded holder and theholder into a predetermined deployment site, wherein the holder isblowmolded onto an inner surface of the compressed state, the holdercontacting the inner surface and at least portions of side surfaces ofthe stent, the holder and the stent thereby having an interference fittherebetween; releasing the stent from interference with the holder; andexpanding the stent from the compressed stent to the expanded stent. 2.The method of claim 1, further comprising: providing a container insidethe holder; supplying a quantity of liquid into the container; andstimulating an inner surface of the holder in response to an increasedpressure of the container, wherein the increased pressure is responsiveto supply of the liquid.
 3. The method of claim 1, further comprising:providing a stimulator attached to a wire inside of the holder, the wireextending from a proximal end to a distal end; delivering the compressedstent and the holder to the deployment site by threading the wirethrough an interior of the holder; and stimulating an inner surface ofthe holder by retracting the stimulator toward the proximal end, whereina diameter of the stimulator is larger than an inner diameter of theholder.
 4. The method of claim 1, further comprising: (a) delivering aplurality of stents in the compressed state and the holder to apredetermined deployment site; (b) retracting the sheath toward aproximal end to the extent that a first stent is exposed wherein thefirst stent is disposed distally adjacent a distal end; (c) expandingthe first stent from the compressed state to the expanded state; (d)retracting the sheath toward the proximal end to the extent that asecond stent is exposed wherein the second stent is disposed proximallyadjacent the first stent; and, (e) repeating steps (a)-(d) untilremaining stents are expanded.
 5. The method of claim 4, wherein theblowmolded holder temporarily restrains expansion of each stent wheneach stent is exposed by the retraction of the sheath.
 6. A method fordeploying a sheathless stent delivery system comprising a stent disposedon a blowmolded holder wherein the stent is configured to expand from acompressed state to an expanded state, wherein the blowmolded holder ofthe sheathless stent delivery system comprises: a cylindrical body; anda plurality of edges integrally formed with the cylindrical body and twoneighboring edges extending toward a strut of the stent and wrappingaround at least a portion of the strut of the stent on opposite sides ofthe strut, wherein the edges radially inwardly press over the stent andcontact a portion of a radially outwardly exposed side surface of thestrut of the stent and simultaneously restricts longitudinal movement ofthe stent relative to the holder; wherein a selected diameter of theholder at the edges is approximately the same as an outer diameter ofthe stent as a whole in the compressed state; the method comprising:delivering the compressed stent and the holder to a deployment site bythreading the holder over a wire through an interior of the holder,releasing the stent from interference with the blowmolded holder byusing a stimulator; and expanding the stent from the compressed stent tothe expanded stent.
 7. The method of claim 6, wherein releasing thestent further comprises releasing the stent from the holder by flexingthe edges without substantially expanding the cylindrical body of theholder, thereby expanding the stent to the expanded state.
 8. The methodof claim 6, wherein releasing the stent further comprises: delivering aspacer attached to a wire to a predetermined deployment site, the wireextending from a proximal end to a distal end; stimulating an innersurface of the holder by retracting the spacer through the holder towardthe proximal end, wherein a diameter of the spacer is larger than aninner diameter of the holder.
 9. The method of claim 6, whereinreleasing the stent further comprises: providing a container inside theholder; supplying a quantity of liquid into the container; andstimulating an inner surface of the holder in response to an increasedpressure of the container, wherein the increased pressure is responsiveto supply of the liquid.
 10. The method of claim 6, wherein releasingthe stent further comprises: providing a stimulator attached to a wireinside of the holder, the wire extending from a proximal end to a distalend; stimulating an inner surface of the holder by retracting thestimulator toward the proximal end, wherein a diameter of the stimulatoris larger than an inner diameter of the holder.
 11. The method of claim6, further comprising: (a) delivering a plurality of stents in thecompressed state and the holder to a predetermined deployment site; (b)retracting the sheath toward a proximal end to the extent that a firststent is exposed wherein the first stent is disposed distally adjacent adistal end; (c) expanding the first stent from the compressed state tothe expanded state; (d) retracting the sheath toward the proximal end tothe extent that a second stent is exposed wherein the second stent isdisposed proximally adjacent the first stent; and, (e) repeating stepsof (a)-(d) until remaining stents are expanded.
 12. The method of claim11, wherein the blowmolded holder temporarily restrains expansion ofeach stent when each stent is exposed by the retraction of the sheath.13. The method of claim 6, wherein the sheathless stent delivery systemhas a low profile whose outer diameter ranges between 0.040 and 0.060.14. A method for deploying a sheathless stent delivery system comprisinga stent disposed on a blowmolded holder wherein the stent is configuredto expand from a compressed state to an expanded state, wherein theblowmolded holder of the sheathless stent delivery system comprises: acylindrical body; and a plurality of patterns or impressions integrallyformed with an outer diameter of the cylindrical body, the plurality ofpatterns or impressions wrapping around at least a portion of a strut ofthe stent in the compressed state with a first edge and a second edge oftwo neighboring patterns or impressions on opposite sides of the strut,wherein the first and the second edges extend toward the strut of thestent disposed between the two neighboring patterns or impressions;wherein the first and the second edges radially inwardly press over thestrut of the stent and contact a portion of a radially outwardly exposedside surface of the strut of the stent and simultaneously restrictslongitudinal movement of the stent relative to the holder; the methodcomprising: delivering the compressed stent and the holder to thedeployment site by threading a wire through an interior of the holder;providing a stimulator attached to the wire to a predetermineddeployment site, the wire extending from a proximal end to a distal end;stimulating an inner surface of the holder by retracting the stimulatortoward the proximal end, wherein a diameter of the stimulator is largerthan an inner diameter of the holder; and releasing the stent frominterference with the blowmolded holder.
 15. The method of claim 14,wherein providing the stimulator comprises: providing a container insidethe holder.
 16. The method of claim 15, wherein releasing the stentfurther comprises: supplying a quantity of liquid into the container;and wherein stimulating the inner surface of the holder furthercomprises stimulating the inner surface of the holder in response to anincreased pressure of the container, wherein the increased pressure isresponsive to supply of the liquid.
 17. The method of claim 14, whereinreleasing the stent further comprises: releasing the stent from theholder by flexing the edges without substantially expanding thecylindrical body of the holder, thereby expanding the stent to theexpanded state.
 18. The method of claim 14, wherein the sheathless stentdelivery system has a low profile whose outer diameter ranges between0.040 and 0.060.
 19. The method of claim 14, wherein the stimulatorcomprises a ball having a diameter larger than an inner diameter of theholder.